Doubt that. Once the transfer is through it's through. Going to be very difficult for her to prove the deceased knew about a crack or any other structural damage. Besides it will take months.
If the transfer hasn't gone through yet, sure she can get out of it.
Also, a 3rd party company damaging the house by fumigating it doing any other work has nothing to do with the sale, or offer to purchase.
If you have a few bucks on the side, always get a structural engineer to check out the house you want to buy. Besides, if it's a vertical crack, if you can't shake hands through it there is nothing to worry about